ClearOS provides both POP and IMAP servers (cyrus-imapd) for providing mail delivery to desktop clients.

If you did not select this module to be included during the installation process, you must first install the module.

You can find this feature in the menu system at the following location:

<navigation>Server|Messaging|IMAP and POP Server</navigation>

The base mail domain is used by a number of apps: SMTP Server, IMAP, Mail Filter, etc. Each app saves this information in its own configuration file, but we really only want to see the domain in one place in the user interface. That's where the Mail Settings app comes in.

• Go to <navigation>System|Account Manager|Account Manager</navigation> to make sure the accounts system (users/groups) is running.

• Go to <navigation>System|Settings|Mail Settings</navigation> to set the mail domain.

• Go to <navigation>System|Accounts|Users</navigation> to create a few users. Please make sure the SMTP Server User and IMAP and POP Server User are enabled for the user.

• Go to <navigation>System|Accounts|Groups</navigation> to create a group or two. You will see a new option when adding/editing a group: Distribution List. If you leave this option enabled, the group becomes a mail distribution list (e.g. sales@example.com will go to all the members of the sales group).

• Go to <navigation>Server|Messaging|IMAP and POP Server</navigation> and start all the servers (if not running).

The mail server supports four different protocols:

• IMAP
• Secure IMAP
• POP
• Secure POP

We strongly suggest using the secure protocols if possible. The IMAP and POP server will use its own self-signed certificate out of the box. We recommend that you obtain a commercial certificate in conjunction with the Certificate Manager or a free Let's Encrypt Certificate to secure the protocol. Instructions on using the Let's Encrypt certificate are in this HowTo.

Some mail clients support the push e-mail feature (also known as the IMAP Idle feature). With this feature enabled on both the server and client, e-mail will appear in your mailbox as soon as it arrives. This feature is most useful on wireless and handheld devices. The following mail clients are known to support push e-mail (IMAP Idle):

• Thunderbird - Many platforms
• Chattermail - Palm Treo
• FlexMail - Windows Mobile
• K-9 Mail - Android

If you are using Mozilla's Thunderbird, click on <navigation>Tools|Account Settings</navigation>, then select “Server Settings” from the navigation bar. Ensure the Use secure connection (SSL) checkbox is enabled.

For Outlook and Outlook Express, click on <navigation>Tools|Accounts</navigation>, select the account you wish to configure and click on the Properties button.

Next, click on the “Advanced” tab, and ensure the “This server requires a secure connection (SSL)” checkbox is enabled.

For other mail clients, similar set-up/configuration will exist. Please refer to documentation for your mail client for specific instructions.

If you open any incoming POP or IMAP port to the internet, then you are more exposed to user/password hacking so strong passwords are highly recommended. By way of mitigation, it is recommended to install the Attack Detector app and enable it for cyrus-imap. The IPS Updates enabled for IMAP and/or POP are also recommended.

• Adding users to ClearOS
• SMTP Server
• More anti-spam and e-mail defence measures HowTo

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